Re: [BUG] While changing the cpufreq governor, kernel hits a bug in workqueue.c

[Johannes Weiner <hannes@saeurebad.de>]

Hi,

Nageswara R Sastry <rnsastry@linux.vnet.ibm.com> writes:

> Hi Johannes,
>>>> =======================================================
>>>> [ INFO: possible circular locking dependency detected ]
>>>> 2.6.25.7.cpufreq_patch #2
>>>> -------------------------------------------------------
> [...]
>>> Okay, the problem is in cpufreq_conservative.c.  We
>>> cancel_delayed_work_sync() while holding the mutex, but the work itself
>>> tries to grab it and there it deadlocks; lockdep caught that right.
>>>
>>> The hunk for _ondemand is correct, but the one for _conservative is
>>> obviously wrong, sorry :/
>>>
>>> I will whip something up and get back to you.  Thanks a lot for
>>> testing!
>>
>> Could you try the attached patch instead of the one above?
>>
>> Dave, I dropped the mutex-grabbing from the conservative worker function
>> as well as I don't see a reason for it, please correct me if I'm wrong.
>>
>> 	Hannes
>>
>
> The script is running now for more than 6 hours successfully, I will
> continue this and let you know if there are any failures.
>
> * I am seeing the circular locking dependency with the above patch
> too.

Uhm.  Failure or no failure?  A possible dead-lock report _is_ a
failure.  So, do you get one or not?  And if so, could you send me the
dmesg parts?

Thanks a lot,

	Hannes